The present invention relates to machines for gathering paper sheets or the like, and more particularly to improvements in gathering machines of the type wherein a conveyor system advances sheets along an elongated path past a succession of magazines for different types of sheets and each magazine is associated with a transfer device which removes sheets from the magazine and delivers them into the range of the conveyor system so that the latter accumulates piles of dissimilar sheets which are ready for conversion into pamphlets, brochures, books or like products.
It is already known to provide a platform or an analogous support between each transfer device and the conveyor system so that sheets which are delivered by the transfer devices come to rest on the respective platforms prior to being entrained by the conveyor system, namely, by fingers, prongs or analogous entraining elements which are provided on an endless chain or the like and strip the sheets off the respective platforms to transfer them onto partly assembled piles of sheets on an elongated track along which the piles advance toward the discharge end of the gathering machine. Reference may be had to my commonly owned copending application Ser. No. 094,321 filed Nov. 14, 1979 for "Gathering machine for paper sheets or the like".
A drawback of presently known gathering machines is that the orientation of sheets is likely to change during transport from the magazines to the respective platforms, i.e., while the sheets advance with or beyond the components of the transfer devices and before the sheets are actually engaged and entrained by the conveyor system. The likelihood of improper orientation is especially pronounced if the sheets are large or thin and if their weight is low. The orientation of a partly misoriented sheet is likely to change again during removal of such sheet from the respective platform, i.e., during transfer onto the aforementioned track under the action of an oncoming entraining element of the conveyor system. As a rule, such secondary change of orientation will involve turning of sheets in response to acceleration in the longitudinal direction of the conveyor system.
The aforementioned copending application Ser. No. 094,321 further discloses hold-down devices which are associated with the platforms and serve to accelerate the sheets prior to engagement of sheets by the oncoming entraining prongs. The hold-down devices engage the upper sides of sheets on the respective platforms shortly before such sheets are engaged by the oncoming prongs to ensure that the sheets are held in proper positions prior to and/or during transport away from the platforms and onto the track of the conveyor system. The arrangement is preferably such that the hold-down devices orbit along endless paths above the upper sides of the respective platforms. At the same time, the hold-down devices can perform an accelerating action, i.e., they can shift the sheets in the direction of removal from the respective platforms.
A drawback of presently known gathering machines is that relatively large sheets are particularly likely to change their orientation during removal from and/or during delivery onto the platforms. This results in the assembly of unsatisfactory piles wherein the sheets are not accurately alined with each other. The causes of misorientation are numerous. For example, relatively large sheets can be misoriented by the accelerating and hold-down devices of the above outlined character because they do not engage sufficiently large portions of the upper sides of sheets on the respective platforms. Alternatively, or in addition to misorientation under the action of the hold-down devices, relatively large sheets can be misoriented during engagement of their trailing edges by the oncoming prongs of the conveyor system.